With sustained development of the smart card technology, it is desirable that smart cards will have more flexible and richer functions. For instance, besides of the conventional SIM card functions, the SIM card can also work as payment card, access control card, clock card, and so on, which really achieves multi-application card. All these need the smart card operating system supports the contact and non-contact mixed working mode (referred to as mixed working mode).
An obvious difference between the mixed working mode and separated non-contact working mode is that: in the separated non-contact working mode, the system power is offered by the non-contact field, therefore, the system will reset since it is powered on again when the smart card leaves and re-enters the non-contact field; In the mixed working mode, the system power can be provided by the contact power supply, in this condition, the system will not reset when the smart card leaves and re-enters the non-contact field.
According to ISO14443 protocol, the non-contact communication can be divided into two stages identified by the non-contact communication state sign, wherein in the first stage (corresponding to Part 3 of ISO14443 protocol), the terminal equipment inquires the required information for the non-contact communication in the smart card operating system, and the smart card operating system responds to the terminal equipment; In the second stage (corresponding to Part 4 of ISO14443 protocol), the terminal equipment sends 14443-4 command to the smart card operating system, and the smart card operating system in the second stage will not respond to the inquiry from terminal equipment for information required for the non-contact communication. Thus it can be seen that a normal non-contact communication always begins at the first stage, and then enters the second stage.
As described above, in the mixed working mode, system power is supplied by means of contact method, namely, the system power is provided by the contact power supply, and non-contact communication always encounters such a problem.
After the non-contact communication enters the second stage, if the smart card operating system leaves and re-enters the non-contact field, the system will not reset since it is not powered on again, and the system can not find out it has ever left the non-contact field, therefore, the non-contact communication remains in the second stage and cannot start from the first stage, which leads to the failure of the non-contact communication between the system and the terminal equipment.
The above-mentioned problem also exists in smart card operating systems which are powered by fixed power source rather than the non-contact field to support the non-contact communication.